Is there an electrical wizard reading this? Just bought 04 Envoy as is 165K miles. AC fan Speed 5 worked intermittently on AC , 1 - 4 don't at all. Bad HARNESS into RESISTOR MODULE replaced which corrected intermittent problem. Then replaced RESISTOR MODULE. Still no 1 -4. Then replaced SPEED CONTROL MODULE. Still no 1 - 4. Yes, both front and rear fuse block fuses are working...they have to be good to make speed 5 work. One Clue: when switching out of speed 5 to one of the 1 - 4 speeds, speed 5 goes off and 2 warning lights appear on dash: SERVICE 4WD...and ABS.